Wireless radio communications systems may comprise many mobile or portable subscriber units. Each subscriber unit will require a certain grade of service, in order to support the communication requirements of a user of the subscriber unit. Here the ‘grade of service’ may be one or more of coverage, capacity, voice/data quality, or another defined parameter. Particular design constraints and usage scenarios arise with two way radio communication systems, such as TETRA and ASTRO systems, or with systems such as LTE.
‘Mission Critical’ radio communications systems include public safety systems used by police, firefighters, medical and other emergency or security services. ‘Mission Critical’ radio communications systems are often pre-planned to provide sufficient grade of service in a customer-defined area. Effective pre-planning provides a considerable ‘grace’ (margin) in system resources, to mitigate un-planned events. Despite such planning, there are real-life situations where the pre-planned system may fail to perform, which may well occur at a critical time. System coverage may, for example, become an issue inside buildings, particularly on top floors, in underground car parks or in shopping malls or in similar situations. In another example, there may be areas such as forests where the infrastructure of base stations supporting the subscriber units is thinly spread or non-existent, due to the low probability of subscriber units placing calls from such locales.
In one usage scenario, the user of a portable subscriber unit may be a police officer who moves out of range of the base stations of a wireless communication system when chasing a suspect. The officer may not even be aware that she/he is leaving the system coverage. In such situations, there is insufficient time and/or equipment to allow the officer's colleagues to set up a repeater or a gateway to extend coverage. In such cases, it may be of value to the officer to be able to start an emergency call, or to send a status or text message to an individual portable radio or dispatcher, for instance, to inform the officer's colleagues about the location of a suspect. In some such scenarios, it would also be beneficial to keep full connectivity between the officer's subscriber unit and the reminder of a call group or dispatcher. Such connectivity would permit the officer to be notified about the locations of other officers, or to receive commands.
In known systems, users have devised various “work arounds” to lack of coverage. Some users employ “talkaround”. A “talkaround” channel is a channel that operates in simplex mode without benefit of a repeater. Other users switch between digital mode and analogue mode to attempt to extend coverage. However, these modes deliver differing levels of quality, and both modes may not support data. Some firefighters, as users of cellular radio systems, also carry separate cellular phones. Their aim is to hope to be able to make a call on a cellular phone when their dispatch wireless communications device cannot receive an adequate signal due to system outages and/or “dead spots”. However, group calls may be taking place on the dispatch wireless communications device, and may not be available on the cellular phone.
Accordingly, there is a need for a dynamic gateway selection method and system in a wireless communication system.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.